What is better for rendering in cycles? A network? Or a single monster workstation?
That will depend on the task and the level of effort you want to put into it.

If you are rendering an animation then you will easily benefit from using multiple machines, each machine can render a single frame at the same time giving a very linear speedup based on number of machines. There is a network render addon included with blender. You may want to look at Flamenco which is the new render farm being developed for the gooseberry project. You could also manually start each machine with a different range of frames. There are also a few render farms available that you can pay by the hour or some similar metric.

If you are rendering a single image then a single machine is the easy way to go. There is no freely available way to break up a single image to render it on multiple machines, it can be done but currently you will need to break up the image and combine it yourself or create an automated way to do it.

There are no restrictions to number of machines you can use on any of the render farm options.